With the large-scale development of urban construction, sewage pipes or energy (liquefied gas, natural gas, etc.) supply pipes have to be laid in cities. A common method is to bury pipelines by trenching, resulting in environmental pollution, traffic jams and potential safety hazards in construction.
Hence, a trenchless technology, which is a construction technology for laying, repairing and replacing underground pipelines by a rock-soil drilling and tunneling method without trenching the road surface or damaging a large area of the surface layer, has also been developed and applied at present. The trenchless technology has the advantages of short cycle, low cost, low pollution, high safety and the like, and will not affect the normal traffic order.
A horizontal directional drilling method, which is implemented by guiding directional drilling of a drill pipe having a drill bit by a trenchless guide instrument, is widely applied to the trenchless pipe-laying technology. The trenchless guide instrument provides real-time operating conditions, such as depth, pitch and clock direction, of the drill bit, so that an operator on the ground controls the drilling path in real time in order to correct subsequent operations in time, thus to ensure precise orientation according to the established path, and to complete trenchless pipe-laying.
The trenchless guide instrument has been widely applied due to a simple and convenient wireless structure. The instrument system includes an underground probe, a ground tracking receiver and a synchronous display. An operator on the ground operates the tracking receiver to determine a perpendicular release point of the drill bit relative to the ground according to a signal which is transmitted by a probe mounted on an underground drill bit, and the operating conditions are acquired according to radio information, which is transmitted by the probe at this release point, received by the tracking receiver.
During the trenchless-guided construction, the probe of the guide system is mounted in a probe compartment of the drill bit. The probe moves in the stratum along with the drill bit, and measures spatial location information of the drill bit in real time and then transmits the signal to a ground receiving device. The operator on the ground can determine deviation between the actual movement path and the designed path of the drill bit according to the spatial location information of the drill bit measured by the underground probe, and then give commands to drill operators who control the movement direction of the drill bit according to the commands, in order to ensure that the drill bit moves forward according to the designed path.
In today's trenchless industry, the probe is a very important part. The antenna in the probe is required to transmit radio signals as many as possible at lowest energy loss. A probe structure usually includes an ECU, an antenna and batteries, with reference to, for example, a guide positioning method and positioning instrument for horizontal directional drilling disclosed in Chinese Patent CN1769645A, where an underground sensing and transmitting probe, which is formed by sealing two metal shells on two ends and an insulating shell in the middle, is provided inside a guided drilling tool connected to the drill pipe; a power supply is mounted in an inner cavity of the metal shell on one end, a wireless transmitting element is mounted in an inner cavity of the insulated shell, and a circuit board on which a signal processing and transmitting element is provided, a tilt angle sensor, a face angle sensor and a temperature sensor are placed in an inner cavity of the metal shell on the other end, and the wireless transmitting element consists of solenoid coils and ferrite magnets sleeved within the coils.
With regard to the probe mentioned above, because magnetic cores of the antenna (the wireless transmitting element) are integrally made from high-permeability ferric oxide and the ferric oxide material itself is relatively fragile, the magnetic cores are easily cracked after a long period of vibration when the drill bit works, thereby generating higher energy consumption, reducing the emission efficiency of the antenna, and reducing the accuracy of the probe position. In addition, because the probe requires more batteries as an energy source and the transmission power of the antenna is direct proportional to its size, it is unable to maximize both the size of the antenna and the capacity of the power supply (the amount of built-in batteries depends upon the length of the battery compartment) in a limited space of the drill bit (the length of the probe is restricted by the drill bit and cannot be infinitely extended), and there is a trade-off between the size of the antenna and the capacity of the power supply.